The big Z on its shoulder stands for Zanda, because Qukey is the daughter of the owner of a big conglomerate that owns/runs Zanda City.

Its a very high-tuned machine in general, but it was re-tuned by Sopp. Its basically a light weight, High-speed model, built with Qukey's fighting style in mind, which is unique amongst knights (she didn't learn it from a particular style or school)